Imaging element and method of manufacturing the same

ABSTRACT

A solid-state image sensor including a substrate having a photoelectric conversion element disposed therein, the photoelectric conversion element converting an amount of incident light into a charge amount, a memory unit disposed at a side of the photoelectric conversion element, the memory unit receiving the charge amount from the photoelectric conversion element, a first light-shielding section formed at a first side of the memory unit and disposed between the charge accumulation region and the photoelectric conversion element, and a second light-shielding section formed at a second side of the memory unit such that the second side is opposite the first side.

BACKGROUND

The present technology relates to an imaging element and a method ofmanufacturing the same, and more particularly, to an imaging elementthat suppresses an influence of stray light and a method ofmanufacturing the same.

Since CMOS image sensors of the related art generally are rollingshutter type sensors that sequentially read pixels, an image may bedistorted due to differences in exposure timing for each pixel. Toprevent this problem, a global shutter type image sensor in which all ofthe pixels can simultaneously be read by forming charge retention unitsin pixels has been suggested (see Japanese Unexamined Patent ApplicationPublication No. 2008-103647). In a global shutter type image sensor,after all of the pixels are simultaneously read to charge retentionunits, the pixels are sequentially read. Therefore, since an exposuretiming may be common for each pixel, it is possible to preventdistortion from occurring in the image.

SUMMARY

In Japanese Unexamined Patent Application Publication No. 2008-103647,the global shutter type image sensor has been suggested. However, in theglobal shutter type image sensor, it is necessary to form a chargeretention region inside a pixel. For this reason, the layout of thepixel may be restricted. As described in Japanese Unexamined PatentApplication Publication No. 2008-103647, since the charge retentionregion is inside the layout of the pixel, an aperture ratio maydecrease. Thus, there is a concern that the sensitivity of a photodiodemay deteriorate or that the capacity of the photodiode and the chargeretention region may be reduced.

Further, there is a concern that optical noise may be an issue sincelight enters the charge retention region during charge retention. Tosuppress the occurrences of optical noise, it is necessary to reduce thesize of the charge retention region; however, with a smaller chargeretention region, there is a probability that the saturation capacity ofthe charge retention region may deteriorate due to the smaller size ofthe charge retention region.

To prevent such reduction in the sensitivity, Japanese Unexamined PatentApplication Publication No. 2003-31785 suggests a method of using arear-surface illumination type sensor. By using the rear-surfaceillumination type sensor, a wiring layer inside a pixel can be formed onthe rear side of the sensor, and thus vignetting of incident light bythe wiring layer can be suppressed. However, when the charge retentionregion is formed inside a pixel of the rear-surface illumination typesensor, the charge retention region is formed on the front surface sideof a substrate in a deep region of the substrate with respect toincident light. Thus, it may be difficult to prevent light from leakingto the charge retention region.

It is desirable to provide a technology capable of preventing light fromleaking into a charge retention region and suppressing an occurrence ofa virtual image caused by light entering the charge retention region.

In accordance with at least one embodiment of the present invention, asolid-state image sensor is provided, the solid-state image sensorcomprising a substrate having a photoelectric conversion elementdisposed therein, the photoelectric conversion element converting anamount of incident light into a charge amount, a memory unit disposed ata side of the photoelectric conversion element, the memory unitreceiving the charge amount from the photoelectric conversion element, afirst light-shielding section formed at a first side of the memory unitand disposed between the charge accumulation region and thephotoelectric conversion element, and a second light-shielding sectionformed at a second side of the memory unit such that the second side isopposite the first side.

In accordance with at least one embodiment of the present invention anelectronic device is provided, the electronic apparatus including anoptical unit, and a solid-state imaging device comprising unit pixelsarranged in a 2-dimential matrix, wherein each unit pixel comprises asubstrate having a photoelectric conversion element disposed therein,the photoelectric conversion element converting an amount of incidentlight into a charge, a memory unit disposed at a side of thephotoelectric conversion element, the memory unit receiving the chargefrom the photoelectric conversion element, a first light-shieldingsection formed at a first side of the memory unit and disposed betweenthe charge accumulation region and the photoelectric conversion element,and a second light-shielding section formed at a second side of thememory unit such that the second side is opposite the first side.

In accordance with at least one embodiment of the present invention, amethod of manufacturing a solid-state image sensor is provided, themethod comprising the steps of implanting a plurality of isolationregions into a substrate, implanting impurities into the plurality ofisolation regions to form one or more photodiodes, one or more memoryunits, and one or more transfer gates, forming one or more trenches inportions of the substrate in which light-shielding sections are to beformed, embedding a light-shielding material into the one or moretrenches, and wherein a first light-shielding section is formed at afirst side of the memory unit and disposed between a charge accumulationregion and the photodiode and wherein a second light-shielding sectionis formed at a second side of the memory unit such that the second sideis opposite the first side.

According to the embodiments of the present technology, it is possibleto prevent light from leaking into the charge retention region andsuppress an occurrence of a virtual image.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating the configuration of an image sensor;

FIG. 2 is a cross-sectional view illustrating the configuration of aunit pixel;

FIG. 3 is a cross-sectional view illustrating a unit pixel;

FIG. 4 is a cross-sectional view illustrating a unit pixel;

FIG. 5 is a diagram illustrating the configuration of the unit pixel;

FIG. 6 is a circuit diagram illustrating the unit pixel;

FIG. 7 is a diagram illustrating a manufacturing process;

FIG. 8 is a diagram illustrating the manufacturing process;

FIG. 9 is a diagram illustrating the manufacturing process;

FIG. 10 is a diagram illustrating the configuration of a unit pixel;

FIGS. 11A and 11B are cross-sectional views illustrating the unit pixel;

FIGS. 12A and 12B are cross-sectional views illustrating the unit pixel;

FIGS. 13A to 13C are side views illustrating the unit pixel;

FIG. 14 is a diagram illustrating the configuration of a unit pixel;

FIG. 15 is a diagram illustrating the configuration of a unit pixel;

FIG. 16 is a diagram illustrating the configuration of the unit pixel;

FIG. 17 is a diagram illustrating the configuration of a unit pixel;

FIG. 18 is a diagram illustrating the configuration of a unit pixel;

FIG. 19 is a cross-sectional view illustrating the unit pixel;

FIG. 20 is a diagram illustrating the configuration of a unit pixel; and

FIGS. 21A and 21B are cross-sectional views illustrating the unit pixel;and

FIG. 22 is a block diagram illustrating a configuration example of anelectronic apparatus to which the present technology is applied.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, modes (hereinafter, referred to as embodiments) forcarrying out the present technology will be described.

The description will be made in the following order.

1. Configuration of Solid-state Imaging element

2. Configuration of Unit Pixel

3. 1-1st Embodiment of Unit Pixel

4. 1-2nd Embodiment of Unit Pixel

5. Configuration of Upper Surface of Unit Pixel

6. Manufacturing Process

7. Second Embodiment of Unit Pixel

8. Third Embodiment of Unit Pixel

9. Fourth Embodiment of Unit Pixel

10. Fifth Embodiment of Unit Pixel

11. Sixth Embodiment of Unit Pixel

12. Seventh Embodiment of Unit Pixel

13. Electronic Apparatus

Configuration of Solid-State Imaging Element

FIG. 1 is a block diagram illustrating an example of the configurationof a CMOS (Complementary Metal Oxide Semiconductor) image sensor as asolid-state imaging element to which an embodiment of the presenttechnology is applied. A CMOS image sensor 30 includes a pixel arrayunit 41, a vertical driving unit 42, a column processing unit 43, ahorizontal driving unit 44, and a system control unit 45. The pixelarray unit 41, the vertical driving unit 42, the column processing unit43, the horizontal driving unit 44, and the system control unit 45 areformed on a semiconductor substrate (not illustrated).

In the pixel array unit 41, unit pixels, including a photoelectricconversion element that produces a charge amount of optical chargecorresponding to an amount of incident light and accumulates the amountof optical charge therein, are arranged in a 2-dimensional matrix form.Hereinafter, the charge amount of optical charge corresponding to theamount of incident light is simply referred to as “charge.”

In the pixel array unit 41, a pixel driving line 46 is formed for eachrow in the left and right directions (an arrangement direction of thepixels of a pixel row) of the drawing and a vertical signal line 47 isformed for each column in the upper and lower directions (an arrangementdirection of the pixels in a pixel column) of the drawing in the pixelarrangement of the matrix form. One end of the pixel driving line 46 isconnected to an output end corresponding to each row of the verticaldriving unit 42.

The CMOS image sensor 30 further includes a signal processing unit 48and a data storage unit 49. The signal processing unit 48 and the datastorage unit 49 may be configured as an external signal processing unitsuch as a DSP (Digital Signal Processor) provided in a separatesubstrate from the CMOS image sensor 30 or as software, or may, ofcourse, be mounted on the same substrate as the CMOS image sensor 30.

The vertical driving unit 42 is a pixel driving unit that include ashift register or an address decoder and drives each pixel of the pixelarray unit 41 so that the pixels are all simultaneously driven or aredriven in units of rows or the like. Although a specific configurationis not illustrated, the vertical driving unit 42 is configured toinclude a reading scanning system and a flushing scanning system or acollective flushing system and a collective transmission system.

The reading scanning system selectively scans the unit pixels of thepixel array unit 41 in order, in the units of rows, to read signals fromthe unit pixels. In a case of row driving (rolling shutter operation),flushing scanning is performed earlier by a time of a shutter speed thanreading scanning in reading rows subjected to the reading scanning bythe reading scanning system. In a case of global exposure (globalshutter operation), collective flushing is performed earlier by a timeof a shutter speed than collective transmission.

By flushing, unnecessary charge is flushed (reset) from thephotoelectric conversion elements of the unit pixels in the reading row.A so-called electronic shutter operation is performed by flushing(resetting) the unnecessary charge. Here, the electronic shutteroperation refers to an operation of discarding the optical charge of thephotoelectric conversion element and starting a new exposure (startingaccumulation of optical charge).

A signal read through the reading operation by the reading scanningsystem corresponds to an amount of incident light after the immediatelyprevious reading operation or the electronic shutter operation. In acase of row driving, a period from a reading timing by the immediatelyprevious reading operation or a flushing timing by the electronicshutter operation to a reading timing by the current reading operationis an accumulation period (exposure period) of the optical charge in theunit pixel. In a case of global exposure, an accumulation period, alsoknown as an exposure period, comprises a period of time from collectiveflushing to collective.

A pixel signal output from each unit pixel of the pixel row selectivelyscanned by the vertical driving unit 42 is supplied to the columnprocessing unit 43 via each of the vertical signal lines 47. The columnprocessing unit 43 performs predetermined signal processing on the pixelsignal output from each unit pixel in the selected row via the verticalsignal line 47 for each pixel row of the pixel array unit 41 andtemporarily retains the pixel signal subjected to the signal processing.

Specifically, the column processing unit 43 performs at least a noiseremoval process such as a CDS (Correlated Double Sampling) process asthe signal processing. Fixed pattern noise unique to the pixel, such asreset noise or noise due to a variation of a threshold value of anamplification transistor, is removed through the correlated doublesampling process by the column processing unit 43. Further, the columnprocessing unit 43 may have, for example, an AD (analog-digital)conversion function to output a signal level as a digital signal inaddition to the noise removal process.

The horizontal driving unit 44 includes a shift register and/or anaddress decoder and sequentially selects the unit circuits correspondingto the pixel columns of the column processing unit 43. When thehorizontal driving unit 44 performs the selective scanning, the pixelsignals subjected to the signal processing by the column processing unit43 are sequentially output to the signal processing unit 48.

The system control unit 45 includes a timing generator that generatesvarious timing signals and performs driving control on the verticaldriving unit 42, the column processing unit 43, the horizontal drivingunit 44, and the like based on the various timing signals generated bythe timing generator.

The signal processing unit 48 includes at least an addition processingfunction and performs various kinds of signal processing such as anaddition process on the pixel signals output from the column processingunit 43. The data storage unit 49 temporarily stores data necessary insignal processing when the signal processing unit 48 performs the signalprocessing.

Configuration of Unit Pixel

Next, a configuration of unit pixels 50 arranged in a matrix form in thepixel array unit 41 in FIG. 1 will be described. In the unit pixel 50 tobe described below, a light-shielding film is provided to prevent, forexample, an influence of light from a rear surface or an influence oflight from a photodiode. Here, the influence of the light from the rearsurface or the like will be described with reference to FIG. 2. Aconfiguration realized to reduce the influence of the light from therear surface will be described with reference to FIG. 3 and thesubsequent drawings.

FIG. 2 illustrates a perspective diagram when viewed from the sidesurface of the unit pixel 50. In the following description, a surface ofthe unit pixel 50 on the upper side of the drawing is referred to as anupper surface and a surface of the unit pixel 50 on the lower side isreferred to as a lower substrate or a rear surface. The unit pixel 50includes, for example, a photodiode 71 as a photoelectric conversionelement. The photodiode 71 is, for example, an embedded photodiode thatis formed by forming a p-type layer in a p-type well layer formed on ann-type substrate on the front surface side of the substrate andembedding an n-type embedded layer.

An accumulation electrode 73-1 is formed on the upper surface of theunit pixel 50 and a charge accumulation unit 72-1 is formed at the lowerside of the accumulation electrode 73-1. At the lower side of the chargeaccumulation units 72 and at the side surfaces of the photodiode 71,light-shielding films 74-1 and 74-2 are formed from the rear surface. Aninsulation film is formed in each of the peripheries of thelight-shielding films 74-1 and 74-2.

The unit pixel 50 illustrated in FIG. 2 is a rear-surface illuminationtype sensor. The rear-surface illumination type will be described. Ingeneral, since a CMOS image sensor is a rolling shutter type sensor thatsequentially reads pixels, an image may be distorted due to a differencein an exposure timing. As a remedy against this problem, a globalshutter type in which all of the pixels are simultaneously read byforming charge retention units in pixels has been suggested. Accordingto the global shutter type, after all of the pixels are simultaneouslyread to the charge retention units, the pixels can sequentially be read.Therefore, since an exposure timing may be common for each pixel, it ispossible to suppress distortion that occurs in the image.

However, since it is necessary to form a charge retention region insidea pixel, the layout of the pixel may be restricted, and thus an apertureratio may decrease. Additionally, there is a concern that thesensitivity of a photodiode may deteriorate or the capacities of thephotodiode and the charge retention region may deteriorate. Further,there is a concern that optical noise may be an issue since light entersthe charge retention region during charge retention. To suppress theoccurrences of optical noise, it is necessary to reduce the size of thecharge retention region, however, with a smaller charge retentionregion, there is a concern that the saturation capacity of the chargeretention region may deteriorate due to the smaller size of the chargeretention region.

As a remedy against the reduction in the sensitivity, a rear-surfaceillumination type sensor may be used. By using the rear-surfaceillumination type sensor, a wiring layer inside a pixel can be formed onthe rear side of the sensor, and thus vignetting of incident light bythe wiring layer can be suppressed. However, when the charge retentionregion is formed inside a pixel of the rear-surface illumination typesensor, the charge retention region is formed as the charge accumulationunit 72 at the front surface side of a substrate and is formed in a deepregion of the substrate with respect to incident light, as illustratedin FIG. 2. Therefore, it may be difficult to prevent light from leakinginto the charge accumulation unit 72.

In such a sensor, there is a possibility that the light leaking from thephotodiode 71 may enter into the charge accumulation unit 72, when thephotodiode 71 (photoelectric conversion unit) and the chargeaccumulation unit 72 (accumulation unit) are formed on the samesubstrate. When such a situation occurs, there is a possibility that avirtual image may occur causing image distortion.

To prevent such a situation, as described and illustrated in FIG. 2, apart of the substrate between the photodiode 71 and the chargeaccumulation unit 72 is trenched and a material that shields light isembedded in the trenched portion. The trenched portions and thematerials embedded in the trenched portions are indicated by thelight-shielding films 74-1 and 74-2 in FIG. 2.

However, as illustrated in FIG. 2, even in the configuration in which apart of the substrate is trenched and light directed toward the chargeaccumulation unit 72 is shielded, there is a possibility that the lightdirected toward the charge accumulation unit 72 may not be sufficientlyshielded to prevent the light entering the charge accumulation unit 72,and thus image distortion may occur.

1-1St Embodiment of Unit Pixel

Accordingly, as illustrated in FIG. 3, the depth of a portion trenchedfrom a light incident surface is sufficiently deep so that the chargeaccumulation unit 72 is completely covered. As in the unit pixel 50illustrated in FIG. 2, a unit pixel 100 illustrated in FIG. 3 includes aphotodiode 101, charge accumulation units 102-1 and 102-2, andaccumulation electrodes 103-1 and 103-2. The photodiode 101, the chargeaccumulation units 102, and the accumulation electrodes 103 are arrangedat the same positions as the photodiode 71, the charge accumulationunits 72, and the accumulation electrodes 73 of the unit pixel 50illustrated in FIG. 2.

In the unit pixel 100 illustrated in FIG. 3, first, light-shieldingfilms 104-1 and 104-2 are formed on the left side of the photodiode 101in the drawing. The light-shielding film 104-1 is sandwiched between inan insulation film. Likewise, the light-shielding film 104-2 issandwiched in the insulation film. Further, light-shielding films 104-3and 104-4 are formed on the right side of the photodiode 101 in thedrawing. Each of the light-shielding films 104-3 and 104-4 is sandwichedin an insulation film.

In the following description, when it is not necessary to distinguishthe light-shielding films 104-1 to 104-4 from each other, thelight-shielding films 104-1 to 104-4 are described simply as thelight-shielding films 104. The description of other portions will bemade likewise.

The light-shielding films 104 are formed to penetrate from the uppersurface to the lower surface of the unit pixel 100. As illustrated inFIG. 3, the charge accumulation unit 102 is located between thelight-shielding films 104. In other words, the light-shielding film 104is formed between the photodiode 101 and the charge accumulation unit102. Accordingly, it is possible to prevent light from leaking from thephotodiode 101 to the charge accumulation unit 102.

In the unit pixel 100 illustrated in FIG. 3, light-shielding films 105-1and 105-2 are further formed. The light-shielding films 105 are formedon the rear surface of the unit pixel 100. The size of thelight-shielding film 105 is set to be substantially the same as the sizeof a gap between two light-shielding films 104. The light-shielding film105-1 is formed between the light-shielding films 104-1 and 104-2 andthe light-shielding film 105-2 is formed between the light-shieldingfilms 104-3 and 104-4.

The light-shielding film 105 is formed at the lower side of the chargeaccumulation unit 102 to surround the charge accumulation unit 102together with the light-shielding films 104. A configuration is realizedin which the charge accumulation unit 102 is surrounded in a U shape bythe light-shielding films 104 and the light-shielding film 105. In otherwords, the light-shielding film 105 is formed as a cover between thelight-shielding films 104.

Thus, by forming the light-shielding film 105, it is possible to preventlight from the rear surface of the unit pixel 100 from entering thecharge accumulation unit 102.

Since the number of processes for forming the light-shielding films 104and 105 may be small, the light-shielding films 104 and 105 can beformed relatively easily. For example, the light-shielding films 104 canbe formed by trenching the substrate downward (trenching the substrateupward) from the upper surface or the lower surface to penetrate throughthe substrate and filling the trenched portion with a light-shieldingmaterial. Then, by forming the light-shielding films 105 on the lowersurface, it is possible to form the light-shielding films in the Ushape, as illustrated in FIG. 3.

Thus, by forming the light-shielding films 104 and 105, it is possibleto reduce an occurrence of a dark current while preventing stray lightfrom entering into the charge accumulation units 102. Further, since thenumber of processes for forming the light-shielding films 104 and 105may be small, the processes themselves are prevented from becomingcomplicated.

1-2nd Embodiment of Unit Pixel

Next, another configuration of the unit pixel will be described withreference to FIG. 4. Since the arrangement of the electrodes and thelike of a unit pixel 150 illustrated in FIG. 4 is the same as that ofthe unit pixel 100 illustrated in FIG. 3, the description will continueappropriately in comparison to the unit pixel 100 illustrated in FIG. 3.

As in the unit pixel 100 illustrated in FIG. 3, the unit pixel 150illustrated in FIG. 4 includes a photodiode 151, charge accumulationunits 152-1 and 152-2, and accumulation electrodes 153-1 and 153-2. Thephotodiode 151, the charge accumulation units 152, and the accumulationelectrodes 153 are formed at the same respective positions as thephotodiode 101, the charge accumulation units 102, and the accumulationelectrodes 103 of the unit pixel 100 illustrated in FIG. 3.

In the unit pixel 150 illustrated in FIG. 4, first, light-shieldingfilms 154-1 and 154-2 are formed on the left side of the photodiode 151in the drawing. Each of the light-shielding films 154-1 and 154-2 issandwiched in an insulation film. Further, light-shielding films 154-3and 154-4 are formed on the right side of the photodiode 151 in thedrawing. Each of the light-shielding films 154-3 and 154-4 is sandwichedin an insulation film.

The light-shielding films 104 of the unit pixel 100 illustrated in FIG.3 are formed to penetrate from the upper surface to the lower surface.The light-shielding films 154 of the unit pixel 150 illustrated in FIG.4 are the same in that the light-shielding films 154 are formed from theupper surface and the lower surface. However, the light-shielding films154 are different in that the light-shielding films 154 are formed suchthat they penetrate substantially up to halfway through the substrate;that is, a portion of the substrate is not penetrated by thelight-shielding films 154the. Stated another way, the light-shieldingfilms 154 are formed in a lower surface direction from the upper surfaceand are disposed up to halfway through the substrate. To complement thenon-penetrating portions of the substrate, light-shielding films 156-1and 156-2 are formed in the unit pixel 150.

The light-shielding films 156 are light-shielding films formed in anupper surface direction from the lower surface and are disposed up tohalfway through the substrate to be alternately arranged between one ormore light-shielding films 154. The light-shielding films 156 are alsoformed such that the periphery thereof is covered with the insulationfilms. Further, light-shielding films 155 are formed on the lowersurfaces of the light-shielding films 156.

By forming the light-shielding films 154 between the photodiode 151 andthe charge accumulation unit 152, it is possible to prevent light fromleaking from the photodiode 151 to the charge accumulation unit 152.Further, since the light-shielding films 155 and 154 are formed at thelower side of the charge accumulation units 152, it is possible toprevent the stray light from the rear surface of the unit pixels fromentering the charge accumulation units 152.

The light-shielding films 154 and 156 are disposed as to have a positionrelation (overlapping position relation) in which parts of thelight-shielding films overlap with each other. Therefore, even when thelight-shielding films 154 and 156 are formed only up to the halfwayportions of the substrate, there are no portions in which thelight-shielding films practically discontinue. Stated another way,light-shielding films 154 and 156 may be formed such that they arecontinuous; that is, gaps between light-shielding films 154 and 156 areminimized. As in the case in which the light-shielding films arecontinuously formed, it is possible to prevent stray light from enteringthe charge accumulation unit 152.

Since the number of processes for forming the light-shielding films 154to 156 may be small, as apparent from the description of a manufacturingprocess to be described below, the light-shielding films 154 to 156 canbe formed relatively easily.

Thus, by forming the light-shielding films 154 and 155, it is possibleto reduce an occurrence of a dark current while preventing stray lightfrom entering into the charge accumulation unit 152. Further, since thenumber of processes of forming the light-shielding films 154 and 155 isnot numerous, the processes themselves are prevented from becomingcomplicated.

Configuration of Upper Surface of Unit Pixel

The unit pixel 100 illustrated in FIG. 3 and the unit pixel 150illustrated in FIG. 4 are different from each other in the method offorming the light-shielding films, but have the same configuration. Whenviewed from the upper surface, the unit pixels 100 and 150 have theconfiguration illustrated in FIG. 5. Here, the description will be madeusing the unit pixel 150 as an example.

FIG. 5 is a diagram illustrating the configuration of the unit pixel 150illustrated in FIG. 4, when viewed from the upper surface (which is anopposite surface to a light-reception surface). FIG. 6 is a circuitdiagram illustrating the unit pixel 150 illustrated in FIG. 5. Theconfiguration illustrated in FIGS. 5 and 6 is a 2-pixel sharingconfiguration. Here, the description will continue on the assumptionthat the photodiode 151 and a photodiode 161 located on the right sideof the photodiode 151 share a reset gate and the like.

The unit pixel 150 includes the photodiode 151 in the middle portion.However, since the P region is present when viewed from the uppersurface, the photodiode 151 is not viewed directly. In FIG. 5, however,the reference numeral is given to show the position relation with theother portions. A memory unit (MEM) 153-1 is disposed on the left sideof the photodiode 151 in the drawing. The memory unit 153-1 correspondsto the accumulation electrode 153-1 in FIG. 4.

A floating gate (FG) 171, a floating diffusion region (FD) 172, and areset gate (RST) 173 are disposed in a line on the lower side of thememory unit 153-1. The description will continue on the assumption thatthe reset gate 173 is shared by the photodiodes 151 and 161.

A transfer gate (TG) 174 is disposed in a part of the photodiode 151. Awiring 175 is disposed in such a manner as to connect the transfer gate174 to the memory unit 153-1. A memory unit 153-2, a floating gate 181,and a floating diffusion region 182 for the photodiode 161 disposed onthe right side of the photodiode 151 are formed at the right side of thephotodiode 151. An amplification transistor (AMP: amplifier) 176 isformed at the lower side of the floating diffusion region 182. Theamplification transistor 176 is shared by the photodiodes 151 and 161,when shared by a plurality of photodiodes.

The transfer gate 174 of the unit pixel 150 having the above-describedconfiguration transfers charge photoelectrically converted by thephotodiode 151 and accumulated in the photodiode 151 to the memory unit153-1 via the wiring 175, when a driving signal is applied to a gateelectrode. Likewise, a transfer gate 183 transfers chargephotoelectrically converted by the photodiode 161 and accumulated in thephotodiode 161 to the memory unit 153-2 via a wiring 184, when a drivingsignal is applied to a gate electrode.

The memory unit 153-1 is shielded from light by the light-shieldingfilms 154-1 and 154-2. As illustrated in FIG. 5, the light-shieldingfilms 154-1 and 154-2 are formed to surround the memory unit 153-1.Therefore, the memory unit 153-1 is shielded from light by thelight-shielding films 154. As illustrated in FIG. 5, the light-shieldingfilms 154 are sandwiched in the insulation film.

Thus, since the light-shielding film 154-2 is formed between thephotodiode 151 and the memory unit 153-1, the charge from the photodiode151 is transferred via the wiring 175. As will be described below indetail, the wiring 175 may not be formed by omitting parts of theinsulation film and the light-shielding film 154 and forming a transfergate in the omitted portion.

The floating gate 171 of the unit pixel 150 transfers the chargeaccumulated in the memory unit 153-1 to the floating diffusion region172, when a driving signal is applied to the gate electrode of thefloating gate 171. The floating diffusion region 172 is a charge voltageconversion unit formed of an n-type layer and converts the chargetransferred from the memory unit 153-1 into a voltage under the controlof the floating gate 171.

The unit pixel 150 further includes the reset gate 173 and theamplification transistor 176 shared by the photodiode 161. The resetgate 173 is connected between a power supply and the floating diffusionregion 172, and thus resets the floating diffusion region 172 and thefloating diffusion region 182, when a driving signal is applied to agate electrode.

A drain electrode and a gate electrode of the amplification transistor176 are connected to the power supply and the floating diffusion region172, respectively, and the amplification transistor 176 reads thevoltage of the floating diffusion region 172. Although not illustratedin the drawing, the unit pixel 150 also includes a select transistor.For example, a drain electrode and a source electrode of the selecttransistor are connected to a source electrode of the amplificationtransistor 176 and the vertical signal line 47 (FIG. 1), respectively,and the select transistor selects the unit pixel 150 from which a pixelsignal is to be read when a driving signal is applied to a gateelectrode. The select transistor may be configured to be connectedbetween the power supply and the drain electrode of the amplificationtransistor 176.

Thus, the CMOS image sensor 30 (FIG. 1) having the above-describedconfiguration realizes the global shutter operation (global exposure) bystarting simultaneous exposure of all the pixels, ending thesimultaneous exposure of all the pixels, and transferring the chargeaccumulated in the photodiodes 151 to the memory units 153 shielded fromlight. Through the global shutter operation, an image with no distortioncan be captured during an exposure period uniform in all of the pixels.

Manufacturing Process

A process of manufacturing the unit pixel illustrated in FIGS. 4 to 6will be described with reference to FIGS. 7 to 9. The manufacturingprocess to be described with reference to FIGS. 7 to 9 is an example ofa manufacturing process when the light-shielding films 154 are formed inthe portions trenched from the upper surface of the unit pixel 150 andthe light-shielding films 155 are formed in the portions trenched fromthe lower surface of the unit pixel 150, as illustrated in FIG. 4.

In step S1 illustrated in FIG. 7, impurities that serve as P-typeisolation regions are implanted to a Si substrate. In step S2, N-typeimpurities are implanted to regions that serve as the photodiode 151,the memory unit 153, and the transfer gate 174. In step S3, thelight-shielding films 154 starts to be formed by trenching the unitpixel 150 from the upper surface of the unit pixel 150.

That is, in step S3, a surface DTI process is performed by forming thetrenches in the portions in which the light-shielding films 154 are tobe formed. Here, DTI is an abbreviation for Deep Trench Isolation, andDTI from the upper surface of the substrate is appropriately referred toas FDTI which is an abbreviation for Front side Deep Trench Isolation.Further, DTI from the lower surface (light-reception surface) side ofthe substrate is appropriately referred to as BDTI which is anabbreviation for Backside Deep Trench Isolation.

In step S3, the Si substrate is trenched by patterning the Si substrateusing a lithography method and processing the Si substrate using a dryetching method to form the FDTI (the light-shielding films 154). Then,the insulation film is formed in step S4 and a metal material serving asa light-shielding material is embedded in step S5. In step S6, surplusportions of the Si front surface of the metal material embedded to formthe light-shielding films 154 are removed by an etch back (EB) method.Thereafter, annealing is performed at 900° C. or more to reduce a darkcurrent from the trenched portions.

In step S7 (FIG. 8), SiN (silicon nitride film) is formed to prevent themetal material from diffusing. In step S8, the surplus insulation filmis removed. In step S9 to step S11, SiN/SiO₂ of a polySi electrodeformation portion is removed by a lithography method and an etchingmethod to form a poly Si gate (poly silicon gate), and then a gateinsulation film and the poly Si are formed/processed, and thus the gateelectrode is formed.

In step S12 and step S13 (FIG. 9), an upper layer wiring is formed (aBELO (Back End Of Line) is formed), a supporting base is bonded on theupper layer wiring, the wafer is reversed, the rear surface of theoriginal substrate is brought to the front side, the surplus Si ispolished, and thus a substrate thinned up to about 5 um is generated.

In step S14 and step S15, patterning is performed using a lithographymethod and the surplus Si is removed using a dry etching method to formthe light-shielding films 155 (BDTI) from the lower surface of the unitpixel 150. Then, the insulation film is formed, as in the FDTI, a metalmaterial is formed in the portion, and the surplus insulation film isremoved by an EB method.

A width with which the light-shielding film 155 is formed may be formedat a gap larger than a gap between two light-shielding films 154, asillustrated in step S14 and step S15 of FIG. 9. For example, thelight-shielding film 155-1 is formed between the light-shielding films154-1 and 154-2. The width of the light-shielding film 155-1 is formedas a width larger than the gap between the light-shielding films 154-1and 154-2.

Thus, a light-shielding property can be improved by causing the width ofthe BDTI to be larger than the gap between two FDTIs, in other words,overlapping the width of the BDTI on the FDTIs in the horizontaldirection.

Alternatively, as illustrated in step S14′ and step S15′ of FIG. 9, thewidth of the BDTI may be configured not to overlap on the FDTIs in thehorizontal direction. The width of the BDTI illustrated in step S14′ andstep S15′ of FIG. 9 is formed as a gap narrower than the gap between twoFDTIs. For example, the light-shielding film 155-1 is formed between thelight-shielding films 154-1 and 154-2. The width of the light-shieldingfilm 155-1 is formed as a width narrower than the gap between thelight-shielding films 154-1 and 154-2.

Thus, even when the BDTI is formed in this way, the light-shieldingfilms are formed such that the BDTI overlaps with the FDTIs in thevertical direction, and thus the light-shielding performance does notdeteriorate. Further, the light-shielding performance can be improvedwhen the overlapping portion is enlarged in the vertical direction.

Although not illustrated in the drawing, the light-shielding propertymay be improved by directly connecting the BDTI to the FDTIs. That is,as illustrated in FIG. 3, the BDTI and the FDTIs may be continuouslyformed and may be formed as the straight-line light-shielding film 104in the substrate. Such a light-shielding film 104 can be formed topenetrate through the substrate, for example, when the FDTI (thelight-shielding film 104) is formed in step S3 to step S6. Further, theprocesses of step S14 and step S15 of FIG. 9 may be omitted.Accordingly, it is possible to reduce the number of processes.

Second Embodiment of Unit Pixel

In the first embodiment, the example in which the transfer gate 174 andthe memory unit 153-1 are connected to each other via the wiring 175 hasbeen described. In a second embodiment, however, a configuration inwhich the wiring 175 is omitted will be illustrated. FIG. 10 is adiagram illustrating the configuration of a unit pixel according to thesecond embodiment when the unit pixel is viewed from the upper surface(which is an opposite surface to a light-reception surface).

The configuration of a unit pixel 200 illustrated in FIG. 10 isbasically the same as the configuration of the unit pixel 150illustrated in FIG. 5. That is, the unit pixel 200 includes a photodiode201, a transfer gate 202-1, a memory unit 203-1, a floating gate 204-1,a floating diffusion region 205-1, a reset gate 206, and anamplification transistor 207.

The unit pixel 200 illustrated in FIG. 10 is also a 2-pixel sharing typeunit pixel. The reset gate 206 and the amplification transistor 207 areshared by photodiodes 201 and 211. The unit pixel 200 illustrated inFIG. 10 will be compared to the unit pixel 150 illustrated in FIG. 5.

As in the unit pixel 150 illustrated in FIG. 5, in the unit pixel 200illustrated in FIG. 10, the memory unit 203-1, the floating gate 204-1,the floating diffusion region 205-1, and the reset gate 206 are disposedbetween light-shielding films 241-1 and 241-2. Likewise, a memory unit203-2, a floating gate 204-2, a floating diffusion region 205-2, and anamplification transistor 207 are disposed between light-shielding films241-3 and 241-4.

A part of the light-shielding film 241-2 is opened toward the photodiode201, and the transfer gate 202-1 is formed in the opened portion. Thetransfer gate 202-1 can be configured to transfer the charge from thephotodiode 201 to the memory unit 203-1 without passing through awiring, when a part of the light-shielding film 241-2 is formed to beopened, such as shown by the part of the light-shielding film 241-2 thatis open.

Likewise, in another unit pixel, for example, a unit pixel 210, a partof the light-shielding film 241-4 is opened toward the photodiode 211,and the transfer gate 202-2 is formed in the opened portion. Thus, apart of the light-shielding film can be opened and the transfer gate canbe formed in the opened portion.

Thus, when the charge is configured to be transferred from thephotodiode 201 to the memory unit 203-1 without using a wiring, thecharge can be transferred on a silicon substrate and noise rarelyoccurs. Thus, it is possible to reduce an influence of the noise.

FIGS. 11A and 11B are cross-sectional views illustrating the unit pixel200 illustrated in FIG. 10. FIG. 11A is the diagram when the unit pixel200 illustrated in FIG. 10 is viewed from a side surface taken along theline XIA-XIA. FIG. 11B is the diagram when the unit pixel 200illustrated in FIG. 10 is viewed from a side surface taken along theline XIB-XIB.

Since the side view illustrated in FIG. 11A illustrates a portion inwhich the transfer gate 202-1 is located, the light-shielding film 241-2is formed upward from the lower surface of the unit pixel 200, but isconfigured not to be formed up to the upper surface and to be formed upto a halfway portion. Stated another way, the light-shielding film 241-2is formed such that it extends upward from the lower surface of the unitpixel 200 up to substantially half the width of the substrate and/or amidpoint position of the substrate. With regard to the light-shieldingfilm 241-2, the light-shielding film 241-1 is formed to penetrate fromthe lower surface to the upper surface of the unit pixel 200. Thus, thelight-shielding film 241 in the portion in which the transfer gate 202is formed is formed up to the halfway portion of the substrate and theother light-shielding film 241 is formed to penetrate through thesubstrate.

Since the side view illustrated in FIG. 11B illustrates a portion inwhich the transfer gate 202 is not located, the light-shielding films241 are formed to penetrate from the lower surface to the upper surfaceof the substrate. The light-shielding films 241 are the same as, forexample, the light-shielding films 104 described with reference to FIG.3.

As illustrated in FIGS. 11A and 11B, a light-shielding film 251-1 isformed on the lower surface of the substrate between two light-shieldingfilms 241, for example, between the light-shielding films 241-1 and241-2. The light-shielding film 251 is the same as the light-shieldingfilm 105 illustrated in FIG. 3 and is formed to reduce an influence ofunnecessary and/or stray light from the rear surface side.

FIGS. 12A and 12B are diagrams illustrating the configuration of otherlight-shielding films 241. FIG. 12A is a side view illustrating aportion in which the transfer gate 202-1 is located, as in FIG. 11A. Thelight-shielding film 241-1 of the unit pixel 200 illustrated in FIG. 12Ais configured to be formed up to a halfway portion of the substrate fromthe upper surface of the unit pixel 200 in the lower surface direction.With regard to the light-shielding film 241-1, the light-shielding film241-2 is configured not to be formed. Thus, the light-shielding films241 in the portion in which the transfer gate 202 is formed are notformed and the other light-shielding films 241 are formed up to thehalfway portions of the substrate.

Since the side view illustrated in FIG. 12B illustrates a portion inwhich the transfer gate 202 is not located, the light-shielding films241 are formed up to the halfway portions of the substrate from theupper surface of the substrate in the lower surface direction. Thelight-shielding films 241 are the same as, for example, thelight-shielding films 154 described with reference to FIG. 4.

As illustrated in FIGS. 12A and 12B, light-shielding films 261 areformed from the lower surface of the unit pixel 200 in the upper surfacedirection. Thus, as in the case described with reference to FIG. 4, twolight-shielding films 241 oriented from the upper surface to the lowersurface of the substrate and the light-shielding film 261 formed betweenthe two light-shielding films 241 are formed from the lower surface tothe upper surface of the substrate. The light-shielding film 241 in theportion in which the transfer gate 202 is located is configured not tobe formed.

As illustrated in FIGS. 11A and 11B or 12A and 12B, the light-shieldingfilms are formed. In either case, the configuration is realized suchthat stray light can be prevented from entering into the memory unit203.

FIGS. 13A to 13C are side views illustrating the unit pixel 200illustrated in FIG. 10 and side views when viewed from a differentposition from the position of FIG. 11A to FIG. 12B. FIG. 13A is thediagram when the unit pixel 200 illustrated in FIG. 10 is viewed fromthe side surface taken along the line XIIIA-XIIIA. FIG. 13B is thediagram when the unit pixel 200 illustrated in FIG. 10 is viewed fromthe side surface taken along the line XIIIB-XIIIB. FIG. 13C is thediagram when the unit pixel 200 illustrated in FIG. 10 is viewed fromthe side surface taken along the line XIIIC-XIIIC.

As illustrated in FIG. 13A, the light-shielding film 241-3 formedbetween the photodiode 201 and the portion in which the memory unit203-2 or the like is formed is formed up to a halfway portion from theupper surface of the substrate in the lower surface direction. Thelight-shielding film 241-3 is formed by performing trenching from thefront surface of the substrate and filling the trenched portion with alight-shielding material. Further, an insulation film is formed betweenthe light-shielding film 241-3 and the substrate.

As illustrated in FIG. 13B, in a portion in which the memory unit 203-2and the like are formed and a portion between the light-shielding films241-3 and 241-4, a light-shielding film 261-2 is formed up to a halfwayportion from the lower surface of the substrate in the upper surfacedirection. The light-shielding film 261-2 is formed by performingtrenching from the rear surface of the substrate and filling thetrenched portion with a light-shielding material. Further, an insulationfilm is formed between the light-shielding film 261-2 and the substrate.

As illustrated in FIG. 13C, in the light-shielding film 241-4 formedbetween the photodiode 211 and the portion in which the memory unit203-2 and the like is formed, there is a portion which is formed up to ahalfway portion from the upper surface of the substrate and a portionwhich is not formed. The light-shielding film 241-4 is not formed in aportion in which the transfer gate 202-2 or the transfer gate 202-3 (notillustrated in FIG. 10) is located. On the other hand, thelight-shielding film 241-4 is formed in a portion in which the transfergate 202 is not located. The light-shielding film 241-4 is formed byperforming trenching from the front surface of the substrate and fillingthe trenched portion with a light-shielding material. Further, aninsulation film is formed between the light-shielding film 241-4 and thesubstrate.

A light-shielding film 271-1 is formed on the lower side of the transfergate 202-2, in other words, in a portion in which the light-shieldingfilm 241-4 is not present. Likewise, a light-shielding film 271-2 isformed on the lower side of the transfer gate 202-3. As in thelight-shielding film 261 illustrated in FIG. 12B, the light-shieldingfilms 271 are formed by performing trenching from the rear surface ofthe substrate and filling the trenched portions with a light-shieldingmaterial.

Thus, a configuration can be realized in which no light-shielding filmis formed in the portion in which the transfer gate is formed and thetransfer gate and the photodiode can transmit and receive the chargewithout passing through a wiring. Even in this configuration, it ispossible to reduce the influence of stray light on the memory unit 203.Compared to a case in which a wiring is used, it is possible to suppressa dark current occurring from a portion in which the Si substrate andthe wiring are bonded, and thus to obtain an image with less noise.

Third Embodiment of Unit Pixel

FIG. 14 illustrates another configuration of a unit pixel. FIG. 14 is adiagram illustrating the configuration of the unit pixel when the unitpixel according to a third embodiment is viewed from the upper surface(which is an opposite surface to the light-reception surface). Theconfiguration of a unit pixel 300 illustrated in FIG. 14 is basicallythe same as the configuration of the unit pixel 200 illustrated in FIG.10. That is, the unit pixel 300 includes a photodiode 301, a transfergate 302-1, a memory unit 303-1, a floating gate 304-1, a floatingdiffusion region 305-1, a reset gate 306, and an amplificationtransistor 307.

The unit pixel 300 illustrated in FIG. 14 is also a 2-pixel sharing typeunit pixel. The reset gate 306 and the amplification transistor 307 areshared by photodiodes 301 and 311. The unit pixel 300 illustrated inFIG. 14 will be compared to the unit pixel 200 illustrated in FIG. 10.

The positions of the reset gate 306 and the amplification transistor 307of the unit pixel 300 illustrated in FIG. 14 are different from thepositions of the reset gate 206 and the amplification transistor 207 ofthe unit pixel 200 illustrated in FIG. 10. Referring back to FIG. 10,the reset gate 206 of the unit pixel 200 illustrated in FIG. 10 isconfigured to be present between the light-shielding films 241-1 and241-2, and the amplification transistor 207 is configured to be presetbetween the light-shielding films 241-3 and 241-4.

On the other hand, the reset gate 306 and the amplification transistor307 of the unit pixel 300 illustrated in FIG. 14 are formed not betweenlight-shielding films but at positions different from the positions ofthe memory unit 303 and the like. The memory unit 303 and the like arelocated on the right side or the left side of the photodiode 301 in thedrawing and are formed inside the light-shielding region interposedbetween two light-shielding films 341. The reset gate 306 is located onthe upper side of the photodiode 301 in the drawing and theamplification transistor 307 is located on the lower side of thephotodiode 301 in the drawing. That is, the reset gate 306 and theamplification transistor 307 are disposed outside of the light-shieldingregion.

The reset gate 306 or the amplification transistor 307 is turned on fora moment and the charge photoelectrically converted and accumulated byincident light immediately before the turned-on time is discharged.Therefore, even when the reset gate 306 or the amplification transistor307 is disposed outside of the light-shielding region, the influence onother portions is considered to be small.

Further, by forming the reset gate 306 or the amplification transistor307 outside of the light-shielding region and enlarging the size of thememory unit 303 formed inside the light-shielding region, it is possibleto increase an amount of charge which can be accumulated.

Fourth Embodiment of Unit Pixel

FIG. 15 illustrates still another configuration of a unit pixel. FIG. 15is a diagram illustrating the configuration of the unit pixel when theunit pixel according to a fourth embodiment is viewed from the uppersurface (which is an opposite surface to the light-reception surface).That is, the unit pixel 400 illustrated in FIG. 15 includes a photodiode401, a transfer gate 402-1, a memory unit 403-1, a floating gate 404-1,a floating diffusion region 405-1, a reset gate 406, and anamplification transistor 407.

The unit pixel 400 illustrated in FIG. 15 is also a 2-pixel sharing typeunit pixel. The reset gate 406 and the amplification transistor 407 areshared by photodiodes 401 and 411. The arrangement of the respectiveunits of the unit pixel 400 illustrated in FIG. 15 is basically the sameas that of the unit pixel 300 illustrated in FIG. 14.

The reset gate 406 of the unit pixel 400 illustrated in FIG. 15 isformed on the lower side of the photodiode 401 and the amplificationtransistor 407 is formed on the upper side of the photodiode 401. In theunit pixel 400 illustrated in FIG. 15, the reset gate 406 and theamplification transistor 407 are also formed in light-shielding regions.That is, the reset gate 406 is formed inside the light-shielding regioninterposed between light-shielding films 441-1 and 441-2 and theamplification transistor 407 is formed in the light-shielding regioninterposed between light-shielding films 441-2 and 441-3.

The light-shielding films 441 are formed to surround the photodiode 401.In the above-described embodiments, the examples in which thelight-shielding films are formed on two sides of the four sides of thephotodiode have been described. For example, the light-shielding film341-2 is formed on the left side of the photodiode 301 of the unit pixel300 illustrated in FIG. 14 and the light-shielding film 341-3 is formedon the right side of the photodiode 301. However, light-shielding filmsare not formed on the upper and lower sides of the photodiode 301.

On the other hand, the light-shielding films illustrated in FIG. 15 areformed to surround the photodiode. For example, the light-shielding film441-1 is formed to surround the photodiode 401. Likewise, a photodiode412 located on the lower side of the photodiode 401 is surrounded by thelight-shielding film 441-2 and a photodiode 413 located on the upperside of the photodiode 401 is surrounded by the light-shielding film441-3.

Likewise, a photodiode 414 located on the left side of the photodiode401 is surrounded by the light-shielding film 441-4 and a photodiode 415located on the right side of the photodiode 401 is surrounded by thelight-shielding film 441-5.

Thus, since each photodiode is surrounded by the light-shielding film,for example, the memory unit 403 is formed between the light-shieldingfilms 441-1 and 441-4, and thus is formed inside a region shielded fromlight by the two light-shielding films. Accordingly, since stray lightcan be prevented from entering into the memory unit 403, a virtual imageand/or distortion can be prevented.

By utilizing a rectangular shape to surround each photodiode (eachpixel) with the light-shielding film, it is possible to prevent lightfrom leaking between the pixels. That is, a mixed color between thepixels can be prevented.

FIG. 16 is a diagram illustrating the configuration of the unit pixel,when the unit pixel 400 is viewed from the lower surface(light-reception surface). As illustrated in FIG. 16, each photodiode issurrounded by a light-shielding film. A light-shielding film is formedeven in a region interposed between two photodiodes, in other words, aregion interposed between two light-shielding films.

For example, a light-shielding film 461-2 is formed between thelight-shielding films 441-1 and 441-2, and a light-shielding film 461-1is formed between the light-shielding films 441-1 and 441-3. In FIG. 16,light-shielding films 462-1 and 462-2 are also formed in the verticaldirection. Thus, the light-shielding films 461 and 462 are formed in across form on the rear surface.

Thus, portions of the rear surfaces other than the photodiodes arecovered with the light-shielding films. Accordingly, a configuration isrealized such that stray light does not enter the photodiode and thememory unit 403.

The side view of the unit pixel 400 having the above-describedconfiguration is configured as illustrated in, for example, FIG. 11B.When the unit pixel 400 illustrated in FIG. 15 is taken along the lineXIB-XIB and is viewed from the side surface, the light-shielding filmsare formed, as illustrated in FIG. 11B. The light-shielding films may beformed, as illustrated in FIG. 3.

Thus, by forming the light-shielding film 441-1 to surround thephotodiode 401, it is possible to prevent light from entering into thememory unit 403 and to prevent light from leaking between the pixels.Accordingly, it is possible to prevent a virtual image occurring due tothe invasion of light into the memory unit 403 and to prevent a mixedcolor between the pixels.

Fifth Embodiment of Unit Pixel

FIG. 17 illustrates another configuration of the unit pixel. FIG. 17 isa diagram illustrating the configuration of the unit pixel, where theunit pixel according to a fifth embodiment is viewed from the uppersurface (which is an opposite surface to a light-reception surface). Aunit pixel 500 illustrated in FIG. 17 includes a photodiode 501, atransfer gate 502, a memory unit 503, a floating gate 504, a floatingdiffusion region 505, a reset gate 506, and an amplification transistor507.

The configuration illustrated in FIG. 17 is a configuration in which anFD region (floating diffusion region) is shared by four pixels. In theconfiguration illustrated in FIG. 17, the floating diffusion region 505is shared by four pixels of photodiodes 501, 511, 521, and 531. In eachunit pixel illustrated in FIG. 17, the photodiode is surrounded by alight-shielding film, as in the unit pixel 400 illustrated in FIG. 15.However, a part of the light-shielding film is formed to be opened, asin the unit pixel 300 illustrated in FIG. 14.

For example, the photodiode 501 is surrounded by a light-shielding film541, but a part of the light-shielding film 541 is opened, and thetransfer gate 502 is formed in the opened portion. The other photodiodesof FIG. 17 have the same configuration. As described with reference toFIG. 14, since charge can be transferred from the photodiode 501 to thememory unit 503 without using a wiring, it is possible to reduce noisecaused due to a dark current.

As described with reference to FIG. 15, since the periphery of thephotodiode 501 is surrounded by the light-shielding film 541, it ispossible to reduce the influence of stray light on the memory unit 503or the like. In the configuration illustrated in FIG. 17, the floatingdiffusion region 505 is shared by four (2×2) adjacent pixels. Therefore,since the area of the memory unit 503 can be enlarged, it is possible toincrease an amount of charge which can be retained.

Sixth Embodiment of Unit Pixel

FIG. 18 illustrates another configuration of the unit pixel. FIG. 18 isa diagram illustrating the configuration of the unit pixel, when theunit pixel according to a sixth embodiment is viewed from the uppersurface (which is an opposite surface to a light-reception surface). Theconfiguration of a unit pixel 600 illustrated in FIG. 18 is the same asthe configuration of the unit pixel 150 illustrated in FIG. 5. That is,the unit pixel 600 includes a photodiode 601, a transfer gate 602-1, awiring 603-1, a memory unit 604-1, a floating gate 605-1, a floatingdiffusion region 606-1, a reset gate 607, and an amplificationtransistor 608.

The arrangement of each unit of the unit pixel 600 illustrated in FIG.18 is the same as that of the unit pixel 150 illustrated in FIG. 5. Thatis, the unit pixel 600 illustrated in FIG. 18 is the same as the unitpixel 150 illustrated in FIG. 5, when viewed from the upper surface, butis different as follows. In a portion of the photodiode 601 of the unitpixel 600, a trench portion 651 is present and the transfer gate 602-1is disposed in the trench portion 651.

FIG. 19 is a diagram taken along the line XIX-XIX, when the unit pixel600 illustrated in FIG. 18 is viewed from a side surface. Sincelight-shielding films 641, 642, and 643 of the unit pixel 600illustrated in FIG. 19 are formed in the same manner as thelight-shielding films 154, 155, and 156 of the unit pixel 150illustrated in FIG. 4, the description thereof will be omitted.

As illustrated in FIG. 19, the transfer gate 602-1 is formed on theupper side of the photodiode 601 and is formed in the portion of thetrench portion 651. The trench portion 651 is a portion trenched at apredetermined depth from the upper surface of the substrate. Thetransfer gate 602-1 is formed in the trenched portion.

When the light-shielding film 641 is formed, the trenching is performedon the substrate from the upper surface. However, the trench portion 651may be formed at the time of the trenching. For example, in step S3 ofthe manufacturing process described with reference to FIG. 7, thetrenching is performed on the substrate to form the light-shielding film154. At this time, the trench portion 651 may be formed.

Alternatively, in step S8 of the manufacturing process described withreference to FIG. 8, the trenching may be performed on the substrate andthe trench portion 651 may be formed, when the surplus insulation filmis removed or after the surplus insulation film is removed.

Then, by forming the transfer gate 602-1, with a vertical shape in thetrench portion 651 formed in this way, the unit pixel 600 as illustratedin FIG. 19 can be generated.

Thus, by forming the transfer gate 602 in a depth direction and formingthe light-shielding films 641 to 643, it is possible to prevent lightfrom leaking from the Si substrate to the memory unit 604. Further, thetransfer gate 602 may be formed in a straight line shape in the depthdirection (the upper and lower directions in FIG. 19) or may be formedin an L shape, as illustrated in FIG. 19.

Seventh Embodiment of Unit Pixel

FIG. 20 illustrates another configuration of the unit pixel. FIG. 20 isa diagram illustrating the configuration of the unit pixel, when theunit pixel according to a seventh embodiment is viewed from the uppersurface (which is an opposite surface to a light-reception surface). Aunit pixel 700 illustrated in FIG. 20 includes a photodiode 701, atransfer gate 702-1, a memory unit 703-1, a floating gate 704-1, afloating diffusion region 705-1, a reset gate 706, and an amplificationtransistor 707.

As in the unit pixel 600 illustrated in FIG. 18, the unit pixel 700illustrated in FIG. 20 includes a trench portion 751 on the photodiode701, and the transfer gate 702-1 is formed in the trench portion 751.The transfer gate 702-1 is formed in the opened portion of thelight-shielding film 741-2. The configuration in which the transfer gate702-1 is formed in the opened portion of the light-shielding film 741-2is the same as the unit pixel 200 illustrated in FIG. 10. Accordingly,since the charge can be transferred from the photodiode 701 to thememory unit 703-1 without passing through a wiring, there are advantagessuch as a reduced occurrence of noise and a reduced influence of thenoise.

As in the unit pixel 300 illustrated in FIG. 14, in the unit pixel 700illustrated in FIG. 20, the reset gate 706 and the amplificationtransistor 707 are disposed outside of a light-shielding region. Asdescribed with reference to FIG. 14, even when the reset gate 706 andthe amplification transistor 707 are disposed outside of thelight-shielding region, the reset gate 706 or the amplificationtransistor 707 is turned on for a moment and the chargephotoelectrically converted and accumulated by light immediately beforethe time of turn-on is discharged. Therefore, the influence on otherportions is considered to be small.

Further, by forming the reset gate 706 or the amplification transistor707 outside of the light-shielding region, the size of the memory unit703 formed inside the light-shielding region can be enlarged, and thusit is possible to increase an amount of charge which can be accumulated.

FIG. 21A is a diagram taken along the line XXIA-XXIA, when the unitpixel 700 illustrated in FIG. 20 is viewed from the side surface. FIG.21B is a diagram taken along the line XXIB-XXIB, when the unit pixel 700illustrated in FIG. 20 is viewed from the side surface. Since thelight-shielding films 741 and 742 of the unit pixel 700 illustrated inFIG. 21 are formed in the same manner as the light-shielding films 241and 261 of the unit pixel 200 illustrated in FIG. 12, the descriptionthereof will be omitted. Light-shielding films 743 are formed on therear surface side of the unit pixel 700 illustrated in FIGS. 21A and21B.

The configuration in which the light-shielding films are formed is thesame as the configuration described with reference to FIGS. 12A and 12Band the like, but is different in that a trench portion 751 is formed inthe unit pixel 700 illustrated in FIG. 21. Referring to FIG. 21A, thetrench portion 751 is formed at a predetermined depth on the upper sideof the photodiode 701. The transfer gate 702-1 with an L shape is formedin the trench portion 751.

Since the transfer gate 702-1 is formed in the opened portion of thelight-shielding film 741-2, as illustrated in FIG. 21A, thelight-shielding film 741-2 is configured not to be formed in the portionin which the transfer gate 702-1 is present.

On the other hand, the light-shielding film 741-2 is configured to beformed in the portion in which the transfer gate 702-1 is not present,as illustrated in FIG. 21B.

Thus, a part of the light-shielding film 741 is opened. Thus, by formingthe transfer gate 702 with the vertical shape in the opened portion andforming the light-shielding film 741 besides the portion in which thetransfer gate 702 is formed, it is possible to prevent light fromleaking from the Si substrate into the memory unit 703.

The transfer gate 702 may be formed of, for example, poly Si(polysilicon) or may be formed of a metal material. For example, morestray light entering into the memory unit 703 can be reduced when thetransfer gate 702 is formed of a metal material than when the transfergate 702 is configured to be formed of polysilicon.

The position of the transfer gate 702 may be in a corner portion of thephotodiode 701 or may be in the middle portion of the photodiode 701. Bydisposing the transfer gate 702 in the middle portion of the photodiode701, the distance between the photodiode 701 and the transfer gate 702can be equally maintained. Therefore, it is possible to obtain theadvantage of easily reading the charge. Further, even when the transfergate 702 is disposed in the middle portion of the photodiode 701, thefact that the light can be prevented from entering into the memory unit703 is not changed.

It is to be noted that the embodiments of the present technology areapplicable to general electronic apparatuses that use the solid-stateimage pickup device in an image reading section (photoelectricconversion element). Examples of such electronic apparatuses mayinclude: image pickup apparatuses such as digital still cameras andvideo camcorders; portable terminal apparatuses that have an imagepickup function; and copy machines that use the solid-state image pickupdevice in the image reading section. The solid-state image pickup devicemay be formed as one chip, or may be in a module-like form having animage pickup function in which an image pickup section and a signalprocessing section are packaged together or in which an image pickupsection and an optical system are packaged together.

FIG. 22 is a diagram illustrating a configuration example of an imagepickup apparatus as an electronic apparatus to which the above-describedembodiments of the present technology is applied.

An image pickup apparatus 1501 shown in FIG. 22 includes an opticalsection 1511 including lens groups etc., a solid-state image pickupdevice (image pickup device) 1512, and a DSP (Digital Signal Processor)circuit 1513 that is a camera signal processing circuit. Further, theimage pickup apparatus 1501 also includes a frame memory 1514, a displaysection 1515, a record section 1516, an operation section 1517, and apower source section 1518. The DSP circuit 1513, the frame memory 1514,the display section 1515, the record section 1516, the operation section1517, and the power source section 1518 are connected to one another viaa bus line 1519.

The optical section 1511 takes in incident light (image light) from asubject and forms an image on an image pickup plane of the solid-stateimage pickup device 1512. The solid-state image pickup device 1512converts, into an electric signal, an amount of incident light that isused to form the image on the image pickup plane in a pixel unit, andoutputs the electric signal as a pixel signal. The solid-state imagepickup device 1512 corresponds to the above-described solid-state imagepickup device 11. The display section 1515 may be formed, for example,of a panel-type display such as a liquid crystal panel and an organic EL(Electro Luminescence) panel. The display section 1515 displays movingimage or a still image that has been picked up by the solid-state imagepickup device 1512. The record section 1516 records the moving image orthe still image that has been picked up by the solid-state image pickupdevice 1512 in a recording media such as a video tape and a DVD (DigitalVersatile Disk).

The operation section 1517 gives, based on operation by a user,operation instructions related to various functions of the image pickupapparatus 1501. The power source section 1518 appropriately suppliesvarious power sources that serve as operation power sources of the DSPcircuit 1513, the frame memory 1514, the display section 1515, therecord section 1516, and the operation section 1517 to these targets.

The above embodiments are described referring to the case as an examplein which the embodiments are applied to a CMOS image sensor in whichpixels that detects signal electric charge according to an amount ofvisible light as physical amount are arranged in rows and columns.However, the present technology is not limitedly applied to CMOS imagesensors but is applicable to general solid-image pickup devices.

The above-described embodiments of the present technology is notlimitedly applied to the image pickup device that detects distributionof an amount of incident visible light and picks up the distribution asan image. The above-described embodiments of the present technology isapplicable to a solid-state image pickup device that picks updistribution of incident amount of infrared ray, X-ray, particles, etc.as an image.

According to the embodiments of the present technology, it is possibleto suppress optical noise of the charge retention region (memory unit),while the sensitivity of the photodiode is ensured. The embodiments ofthe present technology can be applied to a global shutter type sensor.Further, since a charge retention region of a sensor can have a largevolume, it is possible to increase the saturation capacity of the chargeretention region.

Embodiments of the present technology are not limited to theabove-described embodiments, but may be modified in various ways withinthe scope of the present technology without departing from the gist ofthe present technology.

The present technology may be configured as follows.

(1)

An imaging element includes: a photoelectric conversion unit; a chargeretention unit that retains charge accumulated in the photoelectricconversion unit; and light-shielding units that are formed on at leasttwo sides of four sides of the photoelectric conversion unit in adirection in which the photoelectric conversion units are adjacent toeach other. The charge retention unit is formed in a region shieldedfrom light by two light-shielding units.

(2)

In the imaging element described in (1), the light-shielding unit may beformed in a substrate in which the photoelectric conversion unit and thecharge retention unit are formed. When the direction in which thephotoelectric conversion units are adjacent to each other is assumed tobe a horizontal direction, the light-shielding unit may be formed in thesubstrate to penetrate therethrough in a vertical direction.

(3)

In the imaging element described in (1) or (2), the light-shielding unitformed on one side of the photoelectric conversion unit may be formed inthe substrate in which the photoelectric conversion unit and the chargeretention unit are formed. When the direction in which the photoelectricconversion units are adjacent to each other is assumed to be ahorizontal direction, the light-shielding unit may be formed in avertical direction. When a surface of the photoelectric conversion uniton which light is incident is assumed to be a rear surface and a surfacefacing the rear surface is assumed to be a front surface, thelight-shielding unit may include a first light-shielding unit formed upto a halfway portion of the substrate from the front surface in thevertical direction and a second light-shielding unit formed up to ahalfway portion of the substrate from the rear surface.

(4)

In the imaging element described in (3), the second light-shielding unitmay be formed between two first light-shielding units. The firstlight-shielding units and the second light-shielding unit may be formedsuch that an overlapping portion is present in the vertical direction.

(5)

The imaging element described in any one of (2) to (4) may furtherinclude a transfer unit that transfers the charge from the photoelectricconversion unit to the charge retention unit. A portion in which thetransfer unit is located may be opened toward the photoelectricconversion unit.

(6)

The imaging element described in any one of (3) to (5) may furtherinclude a transfer unit that transfers the charge from the photoelectricconversion unit to the charge retention unit. The first light-shieldingunit may include an opening in a portion in which the transfer unit islocated.

(7)

The imaging element described in any one of (1) to (6) may furtherinclude a charge voltage unit that converts the charge accumulated inthe charge retention unit into a voltage; a transfer unit that transfersthe charge accumulated in the charge retention unit to the chargevoltage unit; a reset unit that resets the charge voltage unit; and areading unit that reads the voltage of the charge voltage unit. At leastone of the reset unit and the reading unit may be disposed out of theregion shielded from the light by the light-shielding units.

(8)

In the imaging element described in any one of (1) to (7), thelight-shielding units may be formed on four sides of the photoelectricconversion unit in the direction in which the photoelectric conversionunits are adjacent to each other.

(9)

The imaging element described in any one of (1) to (8) may furtherinclude a charge voltage unit that converts the charge accumulated inthe charge accumulation unit into a voltage. The charge voltage unit maybe shared by four adjacent photoelectric conversion units.

(10)

The imaging element described in any one of (1) to (9) may furtherinclude a transfer unit that transfers the charge from the photoelectricconversion unit to the charge retention unit. When the direction inwhich the photoelectric conversion units are adjacent to each other isassumed to be a horizontal direction, the light-shielding unit may beformed in a vertical direction of a substrate in which the photoelectricconversion unit and the charge retention unit are formed. The transferunit may be formed at a position different from the region shielded fromthe light by the two light-shielding units in which the charge retentionunit is formed and in a portion trenched at a predetermined depth in thevertical direction of the substrate.

(11)

In the imaging element described in (10), the light-shielding unit inthe portion in which the transfer unit is located may be opened.

(12)

There is provided a method of manufacturing an imaging element includinga photoelectric conversion unit, a charge retention unit that retainscharge accumulated in the photoelectric conversion unit, andlight-shielding units that are formed on at least two sides of foursides of the photoelectric conversion unit in a direction in which thephotoelectric conversion units are adjacent to each other. The methodincludes: forming the light-shielding unit formed on one side of thephotoelectric conversion unit in a substrate in which the photoelectricconversion unit and the charge retention unit are formed; forming thelight-shielding unit in a vertical direction, when a direction in whichthe photoelectric conversion units are adjacent to each other is assumedto be a horizontal direction; and forming, when a surface of thephotoelectric conversion unit on which light is incident is assumed tobe a rear surface and a surface facing the rear surface is assumed to bea front surface, a first light-shielding unit formed up to a halfwayportion of the substrate from the front surface in the verticaldirection and forming a second light-shielding unit formed up to ahalfway portion of the substrate from the rear surface.

[1]A solid-state image sensor comprising:a substrate having a photoelectric conversion element disposed therein,the photoelectric conversion element converting an amount of incidentlight into a charge amount;a memory unit disposed at a side of the photoelectric conversionelement, the memory unit receiving the charge amount from thephotoelectric conversion element;a first light-shielding section formed at a first side of the memoryunit and disposed between the memory unit and the photoelectricconversion element; anda second light-shielding section formed at a second side of the memoryunit such that the second side is opposite the first side.The solid-state image sensor according to [1], further comprising:a transfer gate at least partially disposed in the photoelectricconversion region, the transfer gate transferring the chargephotoelectrically converted by the photodiode to the memory unit,wherein a wiring layer connects the transfer gate to the memory unitthrough the first light-shielding film.[3]The solid-state image sensor according to [1] or [2], furthercomprising:a transfer gate at least partially disposed in an opening of the firstlight-shielding film, the transfer gate transferring the chargephotoelectrically converted by the photodiode to the memory unit.[4]The solid-state image sensor according to [3], wherein the charge istransferred from the transfer gate to the memory unit on the substrate.[5]The solid-state image sensor according to any one of [1] to [4], furthercomprising:a floating gate, a floating diffusion region, and a reset gate, whereineach of the floating gate, the floating diffusion region, and the resetgate are disposed between the first light shielding section and thesecond light shielding section.[6]The solid-state image sensor according to any one of [1] to [5], furthercomprising:a third light light-shielding section formed at a back surface of thesubstrate, wherein the third light-shielding section is formed to besubstantially equal to a gap between the first light-shielding sectionand the second light-shielding section.[7]The solid-state image sensor according to any one of [1] to [6], whereinat least a portion of the first light-shielding section and a portion ofthe second light-shielding section are formed such that they extenddownward from an upper substrate surface and penetrate substantiallyhalfway through the substrate in a depth direction.[8]The solid-state image sensor according to [7], further comprising:a third light-shielding section alternately arranged between the firstlight shielding section and the second light shielding section.[9]The solid-state image sensor according to any one of [1] to [8], whereinlight received by the photoelectric conversion section is incident atback surface of the substrate.An electronic apparatus including:an optical unit; anda solid-state imaging device comprising unit pixels arranged in a2-dimential matrix, wherein each unit pixel comprises:

-   -   (a) a substrate having a photoelectric conversion element        disposed therein, the photoelectric conversion element        converting an amount of incident light into a charge;    -   (b) a memory unit disposed at a side of the photoelectric        conversion element, the memory unit receiving the charge from        the photoelectric conversion element;    -   (c) a first light-shielding section formed at a first side of        the memory unit and disposed between the memory unit and the        photoelectric conversion element; and    -   (d) a second light-shielding section formed at a second side of        the memory unit such that the second side is opposite the first        side.        [11]        The electronic apparatus according to [10], further comprising:        a transfer gate at least partially disposed in the photoelectric        conversion region, the transfer gate transferring the charge        photoelectrically converted by the photodiode to the memory        unit, wherein a wiring layer connects the transfer gate to the        memory unit through the first light-shielding film.        [12]        The electronic apparatus according to [10] or [11], further        comprising:        a transfer gate at least partially disposed in an opening of the        first light-shielding film, the transfer gate transferring the        charge photoelectrically converted by the photodiode to the        memory unit.        [13]        The electronic apparatus according to [12], wherein the charge        is transferred from the transfer gate to the memory unit on the        substrate.        The electronic apparatus according to any one of [10] to [13],        further comprising:        a floating gate, a floating diffusion region, and a reset gate,        wherein each of the floating gate, the floating diffusion        region, and the reset gate are disposed between the first light        shielding section and the second light shielding section.        [15]        The electronic apparatus according to any one of [10] to [14],        further comprising:        a third light light-shielding section formed at a back surface        of the unit pixel, wherein the third light-shielding section is        formed to be substantially equal to a gap between the first        light-shielding section and the second light-shielding section.        [16]        The electronic apparatus according to any one of [10] to [15],        wherein at least a portion of the first light-shielding section        and the second light-shielding section are formed such that they        extend downward from an upper substrate surface and penetrate        substantially halfway through the substrate in a depth        direction.        [17]        The electronic apparatus according to [16], further comprising:        a third light-shielding section alternately arranged between the        first light shielding section and the second light shielding        section.        [18]        The electronic apparatus according to any one of [10] to [17],        wherein light received by the photoelectric conversion section        is incident at back surface of the substrate and the solid-state        image device is of the global shutter type.        [19]        A method of manufacturing a solid-state image sensor, comprising        the steps of:        implanting a plurality of isolation regions into a substrate;        implanting impurities into the plurality of isolation regions to        form one or more photodiodes, one or more memory units, and one        or more transfer gates;        forming one or more trenches in portions of the substrate in        which light-shielding sections are to be formed;        embedding a light-shielding material into the one or more        trenches; and        wherein a first light-shielding section is formed at a first        side of the memory unit and disposed between a charge        accumulation region and the photodiode and wherein a second        light-shielding section is formed at a second side of the memory        unit such that the second side is opposite the first side.        [20]        The method of manufacturing a solid-state image sensor according        to [19], wherein the transfer gate is at least partially        disposed in the photodiode, the transfer gate transferring the        charge photoelectrically converted by the photodiode to the        memory unit, and wherein a wiring layer is formed to connect the        transfer gate to the memory unit through the first        light-shielding film.        [21]        The method of manufacturing a solid-state image sensor according        to [19] or [20], wherein a transfer gate is at least partially        disposed in an opening of the first light-shielding film, the        transfer gate transferring the charge photoelectrically        converted by the photodiode to the memory unit.        [22]        The method of manufacturing a solid-state image sensor according        to any one of [19] to [21], wherein the charge is transferred        from the transfer gate to the memory unit on the substrate.

The present disclosure contains subject matter related to that disclosedin Japanese Priority Patent Application JP 2012-247581 filed in theJapan Patent Office on Nov. 9, 2012, the entire contents of which arehereby incorporated by reference.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. A solid-state image sensor comprising: asubstrate having a photoelectric conversion element disposed therein,the photoelectric conversion element converting an amount of incidentlight into a charge amount; a memory unit disposed at a side of thephotoelectric conversion element, the memory unit receiving the chargeamount from the photoelectric conversion element; a firstlight-shielding section formed at a first side of the memory unit anddisposed between the memory unit and the photoelectric conversionelement; and a second light-shielding section formed at a second side ofthe memory unit such that the second side is opposite the first side. 2.The solid-state image sensor according to claim 1, further comprising: atransfer gate at least partially disposed in the photoelectricconversion region, the transfer gate transferring the chargephotoelectrically converted by the photodiode to the memory unit,wherein a wiring layer connects the transfer gate to the memory unitthrough the first light-shielding film.
 3. The solid-state image sensoraccording to claim 1, further comprising: a transfer gate at leastpartially disposed in an opening of the first light-shielding film, thetransfer gate transferring the charge photoelectrically converted by thephotodiode to the memory unit.
 4. The solid-state image sensor accordingto claim 3, wherein the charge is transferred from the transfer gate tothe memory unit on the substrate.
 5. The solid-state image sensoraccording to claim 1, further comprising: a floating gate, a floatingdiffusion region, and a reset gate, wherein each of the floating gate,the floating diffusion region, and the reset gate are disposed betweenthe first light shielding section and the second light shieldingsection.
 6. The solid-state image sensor according to claim 1, furthercomprising: a third light light-shielding section formed at a backsurface of the substrate, wherein the third light-shielding section isformed to be substantially equal to a gap between the firstlight-shielding section and the second light-shielding section.
 7. Thesolid-state image sensor according to claim 1, wherein at least aportion of the first light-shielding section and a portion of the secondlight-shielding section are formed such that they extend downward froman upper substrate surface and penetrate substantially halfway throughthe substrate in a depth direction.
 8. The solid-state image sensoraccording to claim 7, further comprising: a third light-shieldingsection alternately arranged between the first light shielding sectionand the second light shielding section.
 9. The solid-state image sensoraccording to claim 1, wherein light received by the photoelectricconversion section is incident at back surface of the substrate.
 10. Anelectronic apparatus including: an optical unit; and a solid-stateimaging device comprising unit pixels arranged in a 2-dimential matrix,wherein each unit pixel comprises: (e) a substrate having aphotoelectric conversion element disposed therein, the photoelectricconversion element converting an amount of incident light into a charge;(f) a memory unit disposed at a side of the photoelectric conversionelement, the memory unit receiving the charge from the photoelectricconversion element; (g) a first light-shielding section formed at afirst side of the memory unit and disposed between the memory unit andthe photoelectric conversion element; and (h) a second light-shieldingsection formed at a second side of the memory unit such that the secondside is opposite the first side.
 11. The electronic apparatus accordingto claim 10, further comprising: a transfer gate at least partiallydisposed in the photoelectric conversion region, the transfer gatetransferring the charge photoelectrically converted by the photodiode tothe memory unit, wherein a wiring layer connects the transfer gate tothe memory unit through the first light-shielding film.
 12. Theelectronic apparatus according to claim 10, further comprising: atransfer gate at least partially disposed in an opening of the firstlight-shielding film, the transfer gate transferring the chargephotoelectrically converted by the photodiode to the memory unit. 13.The electronic apparatus according to claim 12, wherein the charge istransferred from the transfer gate to the memory unit on the substrate.14. The electronic apparatus according to claim 10, further comprising:a floating gate, a floating diffusion region, and a reset gate, whereineach of the floating gate, the floating diffusion region, and the resetgate are disposed between the first light shielding section and thesecond light shielding section.
 15. The electronic apparatus accordingto claim 10, further comprising: a third light light-shielding sectionformed at a back surface of the unit pixel, wherein the thirdlight-shielding section is formed to be substantially equal to a gapbetween the first light-shielding section and the second light-shieldingsection.
 16. The electronic apparatus according to claim 10, wherein atleast a portion of the first light-shielding section and the secondlight-shielding section are formed such that they extend downward froman upper substrate surface and penetrate substantially halfway throughthe substrate in a depth direction.
 17. The electronic apparatusaccording to claim 16, further comprising: a third light-shieldingsection alternately arranged between the first light shielding sectionand the second light shielding section.
 18. The electronic apparatusaccording to claim 10, wherein light received by the photoelectricconversion section is incident at back surface of the substrate and thesolid-state image device is of the global shutter type.
 19. A method ofmanufacturing a solid-state image sensor, comprising the steps of:implanting a plurality of isolation regions into a substrate; implantingimpurities into the plurality of isolation regions to form one or morephotodiodes, one or more memory units, and one or more transfer gates;forming one or more trenches in portions of the substrate in whichlight-shielding sections are to be formed; embedding a light-shieldingmaterial into the one or more trenches; and wherein a firstlight-shielding section is formed at a first side of the memory unit anddisposed between a charge accumulation region and the photodiode andwherein a second light-shielding section is formed at a second side ofthe memory unit such that the second side is opposite the first side.20. The method of manufacturing a solid-state image sensor according toclaim 19, wherein the transfer gate is at least partially disposed inthe photodiode, the transfer gate transferring the chargephotoelectrically converted by the photodiode to the memory unit, andwherein a wiring layer is formed to connect the transfer gate to thememory unit through the first light-shielding film.
 21. The method ofmanufacturing a solid-state image sensor according to claim 19, whereina transfer gate is at least partially disposed in an opening of thefirst light-shielding film, the transfer gate transferring the chargephotoelectrically converted by the photodiode to the memory unit. 22.The method of manufacturing a solid-state image sensor according toclaim 21, wherein the charge is transferred from the transfer gate tothe memory unit on the substrate.